Cosa Nostra: A History of the Sicilian Mafia by John Dickie 352pp, Hodder, £20

In 1981, the Corleone family of the Sicilian mafia went to war. Within two years, hundreds of mafiosi had been savagely murdered, along with women and children, relatives and friends. Men were shot in public places or strangled in deserted cabins, their bodies dissolved in acid, dropped in the sea, buried in concrete or fed to pigs. The killing had begun in 1979 with attacks on representatives of the state: politicians, magistrates, policemen, even journalists - anyone who refused to use public office in the service of the mafia was bombed or blasted with shotguns.

This mass execution was the culmination of years of preparation by the Corleonesi under the leadership of Luciano Leggio and his lieutenant Totò Riina, whose death squads hunted down their enemies, with the aim of establishing a mafia dictatorship. With this unprecedented bloodshed, the true nature of Cosa Nostra was revealed as a sophisticated and ruthless killing machine.

In this excellent history, John Dickie examines the creation of the Cosa Nostra brand, which, from its inception in the 1860s, marketed itself as a "violence industry". In doing so, he expertly dispels the myth of an old-style mafia characterised by a peculiarly Sicilian sense of pride and honour, a sentimental construct described as "rustic chivalry".

In the years after the unification of Italy in 1860, the state was woefully inadequate in enforcing law and order on the island, and violence had become an essential asset in any Sicilian business enterprise; the ability to use force was as important as having capital to invest. Indeed, violence itself had become a form of capital.

In this fundamental principle, the organisation has changed little in a century and a half. It emerged, as it remains, in the areas where Sicily's wealth was concentrated, squeezing profitable businesses through its protection rackets.

The violence industry reached its apogee in the mass extermination of the early 1980s, when the creation of so many "excellent cadavers" provoked a long overdue intervention by the state. The judiciary's response to the murders of their colleagues was to set up an anti-mafia "pool" of dedicated, highly specialised investigators, led by Giovanni Falcone and Paolo Borsellino, whose work resulted in what became known as the "maxi-trial", with more than 400 captured mafiosi in reinforced cages. The 360 guilty verdicts were hailed as a triumph for law-abiding Sicilians, but the celebrations were short-lived: the judgments were overturned on appeal and the anti-mafia "pool" disbanded. It was only after Falcone took up a position in the ministry of justice and pushed through vital reforms, upholding the original maxi-trial verdicts and creating a new national body dedicated to fighting the mafia, that, for the first time since Mussolini declared war on Cosa Nostra, the organisation seemed to be facing defeat.

Sensing his organisation was under threat, Riina, the boss of bosses, unleashed his rage. Within a few months of the reforms, Falcone and Borsellino were dead. The myth of "rustic chivalry", of the mafia as a force for honour and justice, died with them.

Far from troubling itself with honourable tradition, the mafia has proved highly pragmatic, exhibiting an unscrupulous attitude to political ideologies and making purely tactical alliances; treating public resources with the utmost cynicism, plundering water sources, hospitals and schools. Dickie writes: "The world has changed but the Sicilian mafia has merely adapted; it is today what it has been since it was born: a sworn secret society that pursues power and money by cultivating the art of killing people and getting away with it."

The history of Sicily can read like an endless bloody roll call; the sheer numbers of the fallen and their brutal ends are liable to obscure the finer details. Dickie avoids this by using the now extensive volumes of confessions of penitent mafiosi to reveal their humanity: not as an apologist, but as a way of illuminating what it means to be a member of Cosa Nostra. It was this attention to the human side of mafiosi that made Giovanni Falcone such an effective investigator. Among the confessions of mafia boss Tommaso Buscetta, who, after 40 years in organised crime, declared he would talk - but to Falcone alone - was an explanation of the mafia concept of honour.

This code of honour is behind even the most terrible acts of violence: it permits an initiate to murder even a child if this is deemed necessary for the protection of mafiosi - as it was in the strangling of 13-year-old Giuseppe Di Matteo, the son of a pentito (grass), in 1996. Such a crime, if sanctified by the ruling body or Commission, actually advances the career of the murderer by demonstrating his obedience to the organisation. Within the context of Cosa Nostra, a man becomes inured to abnormal moral standards.

Men of honour are obliged to tell one another the truth, so where possible, they avoid saying anything directly at all. Falcone once told an interviewer: "The interpretation of signs, gestures, messages and silences is one of a man of honour's main activities."

Besides taxing the wits of its members, the mafia's compulsive reticence creates an elaborate code for the historian or reporter to decipher. This is made more complicated by the sometimes maddening Sicilian habit, due no doubt to the danger of talking openly, of circling a subject with hints and elliptical references. Into this fog of allusiveness, Dickie shines a welcome beam of clarity, capturing the mafia's character and modus operandi in a vibrant, muscular and highly readable style.

· Clare Longrigg's Mafia Women is published by Vintage. To order Cosa Nostra for £17 plus p&p call Guardian book service on 0870 066 7979